Beech Removal-Traverse

[Peter]

Ok, heres where I was coming from.

 

Rope tied to top of tree, load hanging directly underneath anchor = 1 unit of load

Rope tied to bottom of tree, run through pulley and load hanging directly below pulley = 2 units of load.

 

Rope tied to top of tree, tensioned for speedline at fall of 30 degrees to horizontal exerts a certain amount of side loading on stem.

 

Rope as above but through pulley at top of tree and tensioned at base of tree exerts less side loading? but more overall force, although some of the forces are redirected.

 

Rope run from ground level up to top pulley, then down again at the same angle, and tensioned from ground level so the tree is in the centre of an equilatral triangle = more force on the line, but most of the force is redirected straight down through the stem, so the loading on the tree is closer to my first example.

 

I could be wrong about this, it is a genuine question.

[Rupe]

I'm unsure too, so am equally happy to learn something.

 

I agree with what your saying peter. If you apply the same load through the pulley then the sideways force is less.

 

But to achieve the same tension in the line (before any load is carried) is less efficient when tensioning at the ground so more force is required overall for the same effect, but yes there still would be less sideways force, and if the ground tensionign was at an oppoiste angle to the load then it would create downward force only.

[scotspine1]

Ok, heres where I was coming from.

 

Rope tied to top of tree, load hanging directly underneath anchor = 1 unit of load

Rope tied to bottom of tree, run through pulley and load hanging directly below pulley = 2 units of load.

 

Rope tied to top of tree, tensioned for speedline at fall of 30 degrees to horizontal exerts a certain amount of side loading on stem.

 

Rope as above but through pulley at top of tree and tensioned at base of tree exerts less side loading? but more overall force, although some of the forces are redirected.

 

Rope run from ground level up to top pulley, then down again at the same angle, and tensioned from ground level so the tree is in the centre of an equilatral triangle = more force on the line, but most of the force is redirected straight down through the stem, so the loading on the tree is closer to my first example.

 

I could be wrong about this, it is a genuine question.

 

Same load in both cases, with Reg's system with the use of a pulley at the top of the tree the load/force is applied more downwards, so less sideloading on the tree -

Edited May 30, 2010 by scotspine1

[Frank]

So if there was something to anchor to an equal distance in the opposite direction of the landing zone and you had a long enough rope you could run from that up to the top of the tree and then down the other side where you want to speedline to making the angle of force nearly straight down?

[scotspine1]

So if there was something to anchor to an equal distance in the opposite direction of the landing zone and you had a long enough rope you could run from that up to the top of the tree and then down the other side where you want to speedline to making the angle of force nearly straight down?

 

In theory yes, but its dangerous to talk about rigging simply in terms of engineering principles. Engineers dont do treework, we do and its our knowledge of the tree and it's condition combined with our knowledge of forces, angles and distances that really counts.

[Frank]

In theory yes, but its dangerous to talk about rigging simply in terms of engineering principles. Engineers dont do treework, we do and its our knowledge of the tree and it's condition combined with our knowledge of forces, angles and distances that really counts.

 

So what you are saying is, reg shoulda just felled it straight through them rhodedendrons, they would have soon sprung back up.

[Frank]

Tim, can you draw a diagram on that welly pic to show what I meant.

[Peter]

A good understanding of the engineering principles helps the arborist to understand the forces exerted on the tree by the rigging operations.

 

A good understanding of tree bio-mechanics helps the arborist to understand what forces the tree will withstand.

 

Both are essential, you shouldnt dismiss the physics too quickly.

[Peter]

Same load in both cases, with Reg's system with the use of a pulley at the top of the tree the load/force is applied more downwards, so less sideloading on the tree -

 

I dont agree.

 

With the rope tied off you have one load/force, with the rope running through the pulley you have two. As you point out, this is mitigated by the redirecting of the load.

[Rupe]

Tims diagram make sense to me, but I sure that more force is required at the base to get the same tension in the rope, so the force now applied at the new angle (red line) is higher than what would have been applied in the first diagram.

 

Taking it further, franks method would work (in reducing sideways pull) but the resulting downward force on the tree would be immense far greater than from simply lowerign a load, so the tree could fail due to the compression force